Order of env variables in sidecontainers changed

[spohner]

We use https://github.com/wrouesnel/postgres_exporter as a global sidecar to export metrics. In the manifest file we define environment variables based on the injected environment variables like this:

env:
- name: DATA_SOURCE_URI
  value: localhost/postgres?sslmode=disable
- name: DATA_SOURCE_USER
  value: $(POSTGRES_USER)
- name: DATA_SOURCE_PASS
  value: $(POSTGRES_PASSWORD)

With the merge of #890 the order of which environment variables are added changed. The order of the env variables is actually a part of the API spec according to kubernetes/kubernetes#40373 (could not find it in the spec docs directly).

By adding the common fields last in the env array a pattern like the one above is no longer supported and this could break some apps.

Should be an easy fix by swapping the order in the append method here

postgres-operator/pkg/cluster/k8sres.go

Line 534 in d52296c

mergedEnv := append(container.Env, env...)

.

I will create a simple PR for this ASAP.

[FxKu]

@fischerman can you also comment on this, as you are using are probably using this feature in prod?

[fischerman]

Makes sense to have the operator environment variables first. Didn't think about that. PR from @spohner looks good!

[frittentheke]

I sent in the PR #946 which sources env variables from a secret. There I particularly allow to "override" certain variables related to backups and buckets - but in general those used by the operator for core functionality should come first if there is not use-case and this would rather create unintended effects.